How to close channel in golang

Golang, as a programming language favored by developers, is also widely used to build high-performance, highly scalable applications. In Golang, channel is a very important feature. Channel, as a way to transfer data between different Go coroutines, is an indispensable part of many Golang applications. At the same time, closing the channel is also a very important operation. Let’s introduce the relevant knowledge points of closing the channel in Golang in detail.

1. Introduction to Channels

First of all, channel is a type-safe, first-in-first-out (FIFO) data structure, which is used as the main synchronization in Golang One of the mechanisms. Channels achieve synchronization through two operations, send and receive operations, similar to pipes. For a single data item of a channel, it is usually called a communication operation (Command).

In Golang, the type of channel needs to be explicitly declared as chan, and it can be declared as a channel of a specific type. Channels are usually created using the make built-in functions.

The following is a simple example:

// 创建整型的通道
c := make(chan int)

In the above code, we create an integer channel, and then we will perform multiple operations on the channel.

2. Closing Channels

In Golang, you can use the built-in function close() to close a channel. The function of this function is to close the channel. After closing The channel can no longer send or receive operations. Data cannot be sent to a closed channel. Unread data in the closed channel can continue to be read. Reading a closed channel will immediately return a zero value of the channel type.

Here is a simple example:

c := make(chan int)

// 向通道发送数据
go func(c chan int) {
    c <- 1
    c <- 2
    c <- 3
    c <- 4
    c <- 5
    close(c)
}(c)

In the above code, we use the go keyword to create a coroutine to send data to the channel. After sending all the data, we call the built-in function close() to close the channel.

Please note that after closing the channel, we can still read unread data from the closed channel, but it will return a zero value of the channel type. Here is a simple example:

c := make(chan int)

go func(c chan int) {
    c <- 1
    close(c)
}(c)

// 从通道中读取数据
fmt.Println(<-c)
fmt.Println(<-c)

In the above code, we read the value twice from the closed channel c. Since c can no longer be written to after closing the channel, c returns the zero value 0 of the channel type for the second read operation.

3. Checking Whether a Channel is Closed

In Golang, you can use the built-in function closed() to determine whether a channel is closed. When the channel is closed, the closed() function will return true, otherwise it will return false.

The following is a simple example:

//判断通道是否关闭
c := make(chan int)

go func(c chan int) {
    c <- 1
    close(c)
}(c)

if !closed(c) {
    fmt.Println("The channel is still open!")
} else {
    fmt.Println("The channel is already closed!")
}

In the above code, we create a coroutine to send a value to channel c, and then close the channel. In the following code, we determine whether the channel is closed by calling the closed() function.

4. Traverse and read all values ​​in a channel

After a channel is closed, unread values ​​can still be read from it. When reading data from a channel, we can use a for loop to iterate through all the values ​​in the channel.

The following is a simple example:

//遍历通道中的所有值
c := make(chan int)

go func(c chan int) {
    c <- 1
    c <- 2
    c <- 3
    c <- 4
    c <- 5
    close(c)
}(c)

for v := range c {
    fmt.Println(v)
}

In the above example, we send the integer values ​​​​1-5 to channel c in sequence. After closing the channel, we use a for loop to iterate through all the values ​​in the channel and output these values.

Summary

In Golang, channel (Channel) is a very useful feature, which is very practical when transferring data between different Go coroutines. Closing channels (Channels) and determining whether channels are closed (Closed Channels) are also very important operations. Here, we work through multiple examples, hoping to have a deeper understanding of the use of channels in Golang.

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